During the year, Airbus worked with Delta Air Lines on a 150-seat aircraft envisioned and required by the airline. The A320 would carry 150 passengers 1,860 nautical miles (3,440 km) using fuel from wing fuel tanks only.[25] The Dash 200 had more fuel through the activation of centre fuel tank, increasing fuel capacity from 15,590 litres (3,429 imp gal) to 23,430 L (5,154 imp gal), enabling flights with a distance of 2,850 nmi (5,280 km). The aircraft would measure 36.04 m (118 ft 3 in) and 39.24 m (128 ft 9 in), respectively. Airbus then had to decide on a cross-section for the A320. It considered a fuselage diameter of "the Boeing 707 and 727, or do something better". It eventually settled on a wider diameter, with the internal width at 3.7 m (12 ft 2 in),[18] compared to 3.45 m (11 ft 4 in) of the Boeing aircraft. Although heavier, this specification allowed the aircraft to compete more effectively with the 737. The A320 wing went through several stages of design, finally settling on 33.91 m (111 ft 3 in).It is long and thin, offering better aerodynamic efficiency because of the higher aspect ratio than the competition, namely the 737 and MD-80. The cockpit of the A321 is similar to that of the A318, A319 and A320. This layout would be incorporated into the A330, A340, A350 and A380. This "commonality" enables pilots to quickly transition among these aircraft. With the A320, Airbus made a controversial decision. For the first time, digital fly-by-wire (FBW) flight control system would be incorporated into a commercial airliner,although it was previously successfully proven on military fighter aircraft,[such as the Vought F-8 Crusader. Aside from associated reduction in weight and cost, this system would provide flight envelope protection. The pilot, in essence, places inputs into the flight control computer, which interprets these actions and moves the flight control surfaces. FBW also allows Airbus to make flying characteristics to later models.